Tourist plane crashes in Alaska, leaving five dead, one missing

Five people have been killed and one is missing after two seaplanes carrying tourists on a sightseeing trip collided in midair off the coast of Alaska.

Key points:

Neither of the single-engine planes were under air traffic control when they collided

They were taking tourists on a sightseeing flight to the Misty Fjords National Monument

Both aircraft were carrying tourists who were part of a week-long cruise

The US Coast Guard said nine of the 10 people aboard one of the aircraft had been rescued and were receiving medical treatment, but four passengers and the pilot of the other small plane died.

The two aircraft went down in the George Inlet, in the south-east of the state, according to Coast Guard Petty Officer Jon-Paul Rios.

The crash site is in the vicinity of a popular tourist lodge that runs excursions to the nearby Misty Fjords National Monument.

Fourteen of the passengers aboard the planes were part of a week-long cruise that had started in Vancouver.

"We are deeply saddened to report this news and our thoughts and prayers are with those who lost their lives and the families of those impacted by today's accident," cruise operator Princess Cruises said in a statement.

The Department of Foreign Affairs and Trade said it was not aware of any Australians involved in the crash at this time, but "the Australian Consulate-General in Los Angeles is making urgent inquires" to confirm.

One of the aircraft involved was a de Havilland DHC-2 Beaver with five people aboard, and the other was a de Havilland Otter DHC-3 carrying 11 people, US Federal Aviation Administration spokesman Allen Kenitzer said.

Neither of the single-engine planes were under air traffic control when they collided, and circumstances of the crash were not immediately known, Mr Kenitzer said.

A team of federal accident investigators is expected to arrive in Alaska shortly to try to piece together what caused the crash.

The National Transportation Safety Board's investigative 'Go Team', which investigates major accidents, is expected to arrive in Ketchikan on Tuesday afternoon (local time).